This invention relates to a screw centrifuge which comprises a preferably cylindrical clarifying part and a conical desiccating part and is provided with axial supply pipes for a washing liquid and with openings for the passage of the washing liquid into the chamber between the screw drum and the screw core.
Solid bowl screw centrifuges (decanters) are mainly used for separating operations in continuous processes. However, they have also proved to be efficient in a charge operation, because only a relatively small surface is required for installation, no outgoing air is produced during desiccation and the installation and maintenance costs are relatively low.
A problem which often occurs is that the solids have to be washed after separation from the liquid. Decanters have been developed for this purpose, in which washing devices are installed (DE-OS 2,165,508). In this arrangement, the washing device substantially comprises axial supply pipes and openings in the screw core for the passage of the washing liquid into the clarifying chamber. The washing liquid discharges through the openings over the solids.
Furthermore, a decanter with a washing device is known, in which small pipes are radially inserted into the screw body in the conical part, through which the washing liquid is sprayed onto the solids.
According to experience, only relatively poor washing results are obtained using such washing devices in decanters, compared to the results of a pure throughflow experiment. The present invention becomes applicable at this point. An object thereof is to improve the efficiency of washing devices in a decanter by constructive measures.